Giving another person access to your email and calendar can be a useful feature, and is a very common practice in any circumstance where it is appropriate for someone else to manage your personal mailbox (for example, a Personal Assistant). There are a few things you should note before doing this:
The ability to allow another user to manage your mailbox is called “Delegate” access, as you are delegating permissions to another user.
To achieve this, please follow these steps in Outlook:
For further information, please refer to the Microsoft Article: Allow someone else to manage your mail and calendar